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Mr Ngom served as interior minister under former President Abdoulaye Wade

Senegal's police have detained a key ally of former President Abdoulaye Wade for questioning.

Ousmane Ngom, a former interior minister, was arrested in the southern town of Kolda while campaigning for legislative polls due on 1 July.

A BBC reporter says Mr Ngom has been flown back to the capital, Dakar.

President Macky Sall, Senegal's first new leader in 12 years, has launched an investigation into allegations of corruption by the former government.

Cars scandal

The BBC's Mame Less Camara in Dakar says Mr Ngom was arrested because he did not turn up for questioning by prosecutors looking into claims that senior members of Mr Wade's government used their positions for personal gain.

The former minister had previously been criticised in March after police shot and killed at least six opposition supporters demonstrating against Mr Wade's re-election bid.

Several former officials have been questioned by a special court - notably Mr Wade's son, Karim, who many Senegalese believed was being groomed as his father's successor.

The former president himself has not been left untouched and several cars that were bought in his name have been confiscated in a dispute over their lawful owner, Mr Wade or the state.

The opposition says the corruption investigations initiated by President Sall are "biased".

A former close associate of Mr Wade, Mr Sall beat him in the second round after winning the support of other opposition parties

He is Senegal's fourth president since the west African nation gained independence from France in 1960.